1. Field of the Invention
The present invention relates to a protection structure of a circuit board and a liquid crystal display device and their manufacturing method, and more particularly to a protection structure of a circuit board for protecting electronic components mounted on a circuit board fixed to an electronic device from an external force by covering them with a plate-shaped protective cover, a liquid crystal display device provided with such a protection structure, and a manufacturing method for realizing them.
2. Description of the Prior Art
In recent years, as seen in a display device and the like of a personal computer, a number of display devices each using a liquid crystal display device have been increased.
The reason is that a liquid crystal display device is shorter in depth and more advantageous to space saving in comparison with a CRT display device.
A liquid crystal display device has ordinarily a circuit board for driving a liquid crystal mounted in its display device.
With the demands on a thinner and more space-saving liquid crystal display device, it has been necessary to more contrive in mounting of a circuit board for driving a liquid crystal.
And since the manufacturing cost must be reduced, it is required to reduce the number of components and reduce members to be used in cost. FIG. 1 shows schematically a perspective view of an example of a liquid crystal display device mounted with a circuit board for driving a liquid crystal.
Referring to the same Figure, a circuit board 2 is fixed to the inside of a liquid crystal display device 3 by means of an unshown method such as screwing or the like.
On the circuit board, such electronic components forming a liquid crystal driving circuit as an active component like an IC 15, a passive component like a capacitor 16 and the like for example are mounted in a bare state.
When handling such a liquid crystal display device, for example, temporarily storing it, packing it in a package box or unpacking it, an unintended external force applied to components mounted on the circuit board may cause a trouble of deficiency of a component and the like.
All components mounted on the circuit board 2 are not the same in height. Many tall components projecting higher than other components like an electrolytic capacitor 16 for example (see also FIG. 2 described later) are mounted. In case that mounted components are uneven in height in such a way, it may occur to apply an unintended force to a tall component by mistake when attaching a circuit board to a liquid crystal display device and thereby transform, break or pull it off.
And in a manufacturing process of a liquid crystal display device, a liquid crystal display device mounted with a circuit board may be brought into and from a hand truck having partitions like a bookshelf in order to carry or temporarily store it. When bringing it into and from the hand truck, a tall mounted component may be struck against the hand truck to be broken or pulled off.
Further, also in a process of assembling a liquid crystal display device mounted with a circuit board into a cabinet to form a display unit, a similar trouble may occur.
Thereupon, up to now, in order to protect components mounted on a circuit board from an unintended external force as described above, a liquid crystal display device has been mounted with a cover for protecting components mounted on a circuit board.
FIG. 2 shows a side view of an example of a liquid crystal display device mounted with such a protection cover.
Referring to FIG. 2, a circuit board 2 is fixed to the inside of a liquid crystal display device 3 by screwing or the like, and a protection cover 1 is provided so as to cover the circuit board.
The protection cover 1 is made of metal or plastic and is formed in advance into a shape in which a flat plate connects to each other two legs which are bent respectively to be wrong L-shaped (part at the left side of the page) and L-shaped (part at the right side of the same), and is fixed on a liquid crystal display device 3 by the bent portions of the two legs in parallel with the liquid crystal display device.
In order to fix the protection cover 1, a method using a double sided adhesive tape or an adhesive agent, or screwing is used.
An insulating sheet 8 provided between the circuit board 2 and the liquid crystal display device 3 is intended to electrically insulate both of them from each other.
The reason is that since usually the inside of a liquid crystal display device 3 is often made of metal for electromagnetic shielding and the inside of a circuit board 3 has a wiring pattern for forming a circuit formed on it or has a connecting portion of the wiring and the mounted components provided on it, the circuit board 2 and the display device 3 must be insulated from each other. By providing a protection cover 1 as shown in FIG. 2, it is possible to protect components mounted on a circuit board.
In case of a protective cover 1, however, a display unit having a liquid crystal display device assembled in it is made thicker by providing this cover.
This is a problem which cannot be neglected to a liquid crystal display device required to be space-saving.
And this problem results in raising the manufacturing cost due to increasing not only the number of components but also a manufacturing man-hour for mounting a protection cover.